Obesity is costly not only to individuals and to the society. The alarming prevalence of obesity demands interventions that are not only effective in weight control but also practical and have the ability to reach higher percentages of the population. Financial incentives are common tools employed in weight loss programs to increase program reach and adherence. Yet the literature to date has used arbitrarily selective incentives and lacks a systematic approach to understanding the appropriate magnitude, types and timing of incentives that could lead to sustained weight loss. A simple incentive plan in conjunction with minimal weight loss programs (i.e., those provide widely disseminable action planning materials that document safe weight loss, eating, and activity strategies) can be an ideal platform for studying people's response heterogeneity to different incentive designs and can be implemented with few human resources and be scaled to reach large populations. This R21 project proposes to conduct the first study to formally evaluate, within an economic framework integrated with psychological motivation variables, the potential effectiveness of the magnitude, type, and timing of financial incentives in stimulating sustained weight loss in overweight and obese adults on the platform of a minimal weight loss program and the interplay between intrinsic motivation and participant perceptions of different aspects of financial incentives. This study will employ a mail survey of 3,000 overweight and obese adults to administer attribute-based choice (ABC) questions to investigate their willingness to participate in a minimal weight loss program when coupled with a range of potential incentive programs. Treatment Self-Regulation Questions will be included in the survey to assess participant motivation and to provide indicators of the continuum of motivation. This R21 project will provide the much needed data (e.g., ranges of magnitude, type and timing of incentives, distribution of IM effects on people's participation decisions) to calibrate the incentive arms for a full scale R01 study of financial incentives to stimulate sustained weight loss. PUBLIC HEALTH RELEVANCE: In addition to the negative impact obesity has on personal health and quality of life, there is a large economic impact to society in the form of high healthcare costs and reduced productivity at work. Financial rewards are commonly used to help motivate people but only a few studies have shown they work and it is unclear why some financial incentives work and others don't. This project will test the influence of different types of rewards for weight loss and determine the types of incentives that would be most encouraging for overweight and obese individuals to participate in weight loss programs and our findings will help to identify what types of incentives hold promise in achieving significant weight loss.